T-Mobile Data Roaming Question

[IHaveAnAndriod]

U have the nexus 5 on T-Mobile with the $80 unlimited everything plan. I was on the phone with a representative to resolved my internet connectivity issue. The issue was resolved.
The reprehensive told me that date roaming will help me when though I'm on a prepaid account. I thought something was wrong with that. I'm on a prepaid account, how would data roaming help me if T-Mobile can't charge me for overages
Can data roaming really be helping my connectivity or did the representative just tell me that for marketing purposes?

 

[DirtyDee]

honestly I have zero idea, I was told my reduced speeds(their was none btw) was due to my holding on to the 70 unlimited plans. so they may just be trying to bolster numbers.